Low pressure refining and cracking plant for hydrocarbons



Aug. 3, 1943. w. HOMFELDT 2,326,032

LOW PRESSURE REFINING AND CRACKINGPLANT FOR HYDROCARBONS Filed Feb. 25, 1941 2 sheets-Sheet 1 Invfnor WILLIAM HOMFELDT, by www,

Attorney.

Aug- 3 1943 w. HoMFELD-r 2,326,032

y LOW PRESSURE REFINING AND CRACKING PLANT FOR HYDROGARBONS Filed Feb. 25, 1941 2 Sheets-Sheet 2 A l .J\ 5"- 29,

djd 9 3.? $91 w 4:25

l v x n l Inventor: WlLU/Xm HOMFELDT by cui Cl Him/Www,

Attorney.

Patented Aug. 3, 1943 UNITED STATES .PATENT oFFlcE LOW PRESSURE REFINING AND CRACKING PLANT FOB S William Homfeldt, Azcapotzalco, Mexico l Application February 25, 1941, Serial No. 380,558

(Cl. 20L-50) Alclaim.

object to provide a plant which completely re'l fines the crude oil, with perfect control of the temperature in each phase of the process, a continuous automatic operation of the plant, purifying lters fork the elimination of carbonac'eous and other foreign matter from the gasoline, and

a low cost of operation due to the electric heaters employed.

In the accompanying drawings:

Figure 1 is a schematical view of the whole refining plant.

Figure 2 represents schematically the different successive steps of the rening process.

Figure 3 is a sectional view of the cracking tank for gasoline with electric heaters and purifying system.

Figure 4 shows the same tank viewed from above, with the cover partly cut away and demonstrating the arrangement of the heating elements therein.

Figure 5 represents in partial section the inside construction of the electric heaters.

Figure 6 is a partly sectional view, on a bigger scale, of one of the terminals of a. heating element with adjusting means for the electrodes.

As shown in Figure 1, the crude oil is raised by a pump PI through a. pipe 3 to a preheater tank 4, and from this tank it is introduced through a pipe 5 and a spray nozzle 6 (Figure 3) into the cracking tank 1. This tank has preferably a hexagonal shape and is provided inside with electric heaters 8 to be described in detail later, and which are centered by rings 9 of porcelain or other refractory material, in thin copper tubes III passing alternately through different opposite 'walls of the hexagonal body of the tank 1, as shown in Figure 4. Instead of a hexagonal tank, a square or any other polygonal tank may be used. 'I'he poles I3 and I4 of the heating elements 8 are connected by plugs I5 and cables I8 with the switchboard I1. This switchboard is also connected by cables I 8 with the heating elements 8 of the preheater 4 which lsprovided with a thermometer I8. Each heating element 8 of the preheater 4 and of the cracking tank 1 has its own switch I9 on the switchboard I1, which is further provided with a main supply 28 for.

v ous vapors.

the current, a main switch 2 I, a voltmeter 22 and an amperemeter 23.

The cracking tank 1 is closed above and below by two conical covers 24 and 25, the upper cover 24 having a bottom 2B provided with holes 21 for the passage of the gasoline vapors and sulphure- The upper extremity of the cover 24 carries a shortthreaded tube 28 entering a T-connection 30 from which extends laterally the .condenser tube 3| with inner refrigerating coil 32 connected through pipe 32* with the water pump P2. Theupper end of the T 30 is closed by a tubular cap 33 into which enters'laterally the feed pipe 4 conducting the crude oil. The bottom of this cap 33 is provided with perforations 34 for the passage of sulphureous vapors. Above the cap 33 there is a tube or chimney 35 of suitable height through which escape the sul,- phureous vapors', gases, etc., the draft being regu- ,lated by a damper 36. The lower cover 25 has a hexagonal ilange'31 which, as is also the flange 26 of the bottom of the upper cover 24, is fastened by screws to the ilanges 38 and 39 of the tank 1, with packing rings 40 between adjacent flanges.

vInto the upper cover 24 enter a number of pipes 4I descending from a tank 42 containing acids, each pipe 4I being provided with two valves 42' and 42h, in order, during the operation of the plant, to spray acid on the lumps 43 of porous illtering material placed on the perforated plate 25 forming the bottom of the cover 24. On the tank 1 is further mounted a thermometer 44 and a gauge 44Il for controlling the temperature and height of the oil respectively.

The bottom of the lower cover 25 is connected by a pipe 45 with the vaporization tank l46, placed at a lower level than the tank 1 so that the residues of the tank 1 may flow freely and'automatically into the tank 46 during the operation of the plant, as these residues should not stay in the cracking tank (which is easily veried by the gauge 44B) as they would cover the heating tubes I0 and thus would produce an interruption in the cracking process. The vaporization tank 45 has the samekind of heating elements 8 as the tank 1, its tubes I0 having two-pole connections, through conductor cables 41 connected with the switches 48, supply mains 49 with main switch 58, voltmeter 5I and amperemeter 52 in switchboard 53 and has a thermometer 54. The upper cover 56 of the tank 45 is further provided with a manometer 55 indicating the low pressure existing in the plant and is connected with the vaporization pipe 51 provided with a shut-olf valve 58. 'I'he pipe 51 continues upwardly, with another shut-olf valve 59, and together with the chimney 60 serves as an escape for the sulphureousvaporsv and gases which may still be left. The pipe 6I united laterally with the pipe 51 is connected with the circulation pipe 62 serving as a syphon, and the pipe 62.itself is connected with the condenser system 63 receiving water from the pump P2 through the pipe 32B. The pipe 84, with intermediate valve 85, which descends from the circulation pipe 62, returns to the vaporization tank 46. Depending upon the nature or the crude oil' treated, the vaporization plant described Y may be used for obtaining'an intermediate distillate. The lateral pipe 66 for petroleum distillate leaves the vaporization tank 46 at a given Yheight and is provided with a shut-ofi or throttle valve 61. I'he control cock 68 mounted below the pipe 66 permits the withdrawal of petroleum distillate for assaying. The vaporizationytank 46 trol the height of the second residue (gas-oilasphalt) which leaves automatically through the pipe 1I, with intermediate valve 'l2 (the control cock 'I3 serves for extracting samples) .and enters the electrical superheater 14. This nishes the process for the second distillation product (kerosene) and the third process follows, theproduction of gas oil.

The second residue (gas oil-asphalt) ,leaves automatically the vaporization tank 46, *throughv the pipe 1I, and enters the fractionation plant located at a still lower level, passing rstthrough the superheater 'I4 for increasing the temperature, if necessary. The equipment of this tank is the same as in tanks 4, 1 and 46 with respect to heating elements 8 and tubes I0, and it is connected in the same Way with the switchboard l by cables 16. The second residue (gas oila-sphalt) leaving the superheater 14, passes automatically through the pipe 'Il to the fractionation tank.18. The connecting pipe .11 isk provided with a thermometer 19 for reading the higher temperature obtained. The fractionation tank '18, electrically heated, is provided with the same electrical devices as the formerly described tanks, and has its own switchboard 80, thermometer 8l, manometer 82, gauge 83 for indicating the -height of the cracking materiaLthe same type of vaporization system 84 as the vaporization tank 46 already described, its discharge pipe 85 with shut-olf or throttle valve 86 and control cock 81, conducting to the respective refrigeration system, from which issues the gas oil (distillation product G). Finally there is the discharge pipe 88 with corresponding connections for the asphalt (third residue A).

The refining plant described in the foregoing is intended principally for producing three distillation products, i. e. gasoline, kerosene, and gas oil, but, depending upon the nature of the crude oil, the two vaporization devices 46 and 18 may be used for producing also intermediate distillates. In Figure 2 is shown schematically the fractionation oi the crude oil intoits components B (gasoline), P (kerosene), G (gas oil) and A (asphalt), with-the temperatures corresponding to each phase of the process.

Figures 3, 4, 5 and 6 illustrate the electrical heating elements used for heating the dierent fractions of the crude oil in the plant described. These elements employ a granulated resistance material composed of carbon (graphite), Carborundum and clay. For protecting this material against oxydation, it is saturated with solutions of tungsten or molybdenum salts.` This material becomes incandescent when vthe electric currentpasses through it and can produce temperatures up to 3000 C. It has the advantage which the material is placed. the increase in that the vtemperature is easily regulated by I pression to which the material is subjected. The

-temperature of the elements may further be varied by increasing or diminishing the electric current passing through the material, and the temperature may therefore be easily regulated within wide limits by employing one or both methods, i. e. compression of the material and changes in the electric current.

The granulated material a is placed loosely in a tube b of porcelain or other refractory material, surrounded by the iron tube 8 provided with cast on annular rlbs. This tube 8 is placed within the copper tube I0, closed at both ends by caps c. The flanges 8' on the ends of the tube 8 are united by screws, in an insulated manner, with the anges d of tubular members e through which pass the electrodes j, the conical points of which contact the granulated resistance material a of tube b. The closed end of the tubular member e is tapped for the threads of a screw g, one reduced end of which enters the inner extremity of the electrode f and is .held bya lock-nut i. 'I'he end of the'tubular member e is recessed for receiving the threaded end yof a cylinder a', a packing 1c and washer l being -placed between the two parts for providing an air-tight seal. Through this cylinderi also passes thc screw g. The opposite end of the cylinder :i receives a threaded plug m which presses the packing n' around the screw g, forming another air-tight seal. The plain unthreaded end of the screw g passes' through a disc'o of insulating material placed within the cap c and is provided with a hand wheel p also made of insulating material, the extremity of the screw being perforated longitudianlly for receiving the plug l5. Within the copper tube I0, the tubular member e is surrounded by a thick ring r of refractory material which lls the tube I0 and prevents loss of heat from the element.

As the electric current passes through the granulated resistance material described, it becomes incandescent in a` few seconds and the heating begins. The current consumption is in inverse proportion to the consumption in heaters with resistance wires, as in the latter the resistance increases with the temperature While the conducting power of the granulated material is higher with increasing temperatures. It must also be noted that a relatively big element need not receive the electric current constantly, as the resistance material and theinner porcelain tube are bad conductors of heat and therefore conserve the heat during a considerable time.`

The granulated resistance material should always be used in hermetically sealed heaters, like those described above, due to the fact that in these heaters the combustion of the carbon (graphite) is so much reduced that the element will haveto be refilled only after having been used yfor more than six months. Y

The plant described in the foregoing operates as follows:

All the electric heating elements of the difierent tanks are first put in circuit by means of the switches on the respective switchboards. When the desired temperature has been reached in each tank, as shown by the thermometers, the pump P1 for the crude oil and pump P2 for the condensing water are started. The pump P1 raises the crude oil to the preheater 4 where itis heated to make it more iiuid so that it may leave the spray nozzle 6in tank I in a nely divided state and be the oil and enter through the perforated plate 26 into the filter chamber in which they pass between the filter material impregnated with acids and are freed from carbonaceous and other foreign matter, escaping automatically through the condenser tube 3l where they are condensed and cooled before reachingthe storage tank. The sulphureous vapors and other gases formed during the process escape through the chimney 35. The iirst residue (PGA) of the cracking material flows'automatically into the vaporization tank 46 located at a lower level, where the second distillation process, production of kerosene, takes place.

The Vaporization tank 46 employs the same kind of electric heating system as the tank 1, with the diiierence that it contains a greater number of heating elements, as the temperature to be obtained is higher for the separation of petroleum distillate from the first residue. This distillate is discharged automatically through the pipe 66 into its own condenser system.

The second residue (GA) flows through the circulation pipe ll automatically into the fractionation tank 18, placed at a still lower level, where the distillation process is the same as in the vaporization tank 48. If necessary, the temperature of the cracking material GA, after leaving the tank 4G, is increased'in the superheater 14, before it enters the fractionation tank 18 This tank is operated at a still higher temperature, as in this third distillation process the gas oil is separated. Through its discharge pipe the gas oil distillate flows automatically to its condenser system, and the third residue, asphalt and analogous products, is discharged through the pipe 88.

Both the vaporization tank 46 and the fractionation tank 18 are provided with vaporization devices which maybe used simultaneously with the triple cracking process for producing intermediate distillates, depending upon the com position of the crude oil being treated. These intermediate vaporization devices are further provided with chimney or escape pipes for the discharge of sulphureous vapors and gases which may still be present.

What I claim is:

A heater for use in treating oil, said heater comprising a tube of refractory material, a metal tube enclosing said first-named tube, said metal tube having heat-radiating fins thereon, the metal of which the tube and iins are made having a relatively high melting point, an outer tube of metal, said outer tube having a good heat conductivity, a refractory granular electrical resistance material within the innermost tube, said material being composed of graphitic carbon, silicon carbide, and clay, means for protecting said material against oxidation, comprising a refractory coating containing a compound of a metal of the group consisting of molybdenum and tungsten, electrodes in contact with the ends of the column of granular material, and means for varying the pressure of said electrodes'on said material to control the resistance thereof at will.

WILLIAM HOMFELDT. 

